# include <stdio.h>
# include <math.h>

int main(){
    double a,b,c,s,area;
    a=3.67;
    b=5.43;
    c=6.21;
    s=(a+b+c)/2;
    area = sqrt(s*(s-a)*(s-b)*(s-c));
    printf("area=%f", area);
    return 0;
}